Acute pancreatitis is a condition that affects over 200,000 persons annually in the United States. It is characterized by inflammation of the pancreas and severe abdominal pain. In extreme cases the illness can lead to renal and respiratory failure and even death. About 20% of all acute pancreatitis patients are considered idiopathic, that is, there is no known cause for the condition. Up to 75% of the idiopathic pancreatitis cases are associated with the presence of microcalculi, also known as microlithiasis, in the common bile duct. These are small stones believed to cause pancreatitis by transiently blocking the pancreatic duct that empties into the duodenum at the sphincter of Oddi.
To diagnose microlithiasis, patients typically undergo endoscopic retrograde cholangiopancreatography (xe2x80x9cERCPxe2x80x9d) by a gastroenterologist. In this procedure, the patient is sedated, and an endoscope is introduced orally and maneuvered through the stomach to the duodenum at the exit point of the common bile duct. A catheter is introduced into the bile duct through a working channel of the endoscope, and a sample of bile is aspirated from the patient. The patient is then discharged from the hospital and the bile sample is subsequently analyzed by laboratory personnel using a polarization microscope.
The presence of microlithiasis in the bile sample usually requires the pancreatitis patient to undergo further interventional treatment. The preferred treatment is usually a sphincterotomy, an endoscopic procedure in which a cut is made in the sphincter of Oddi to disrupt the sphincter and allow continual drainage of the bile duct. A sphincterotomy in cases of pancreatitis associated with microlithiasis has been shown to reduce the incidence of recurrent pancreatitis from 73% in the absence of a sphincterotomy, to 10% when the procedure has been performed. A sphincterotomy is preferable to the more invasive, involved and costly cholecystectomy, i. e., the surgical excision of the gall bladder.
A disadvantage of the above-described delayed analysis procedure is that the sphincterotomy must be accomplished through a second ERCP after the test result indicating the presence of microlithiasis becomes available. This additional procedure increases the cost of treating the condition and, for a second time, subjects the patient to the inherent risks associated with undergoing ERCP. If the gastroenterologist had knowledge of the presence of microlithiasis at the time of the first ERCP when a bile sample was collected, a sphincterotomy could be performed during the initial ERCP. A device that could make a rapid, intra-operative determination of the presence of microlithiasis could significantly reduce the medical expense when a sphincterotomy is called for.
The protocol for laboratory evaluation of bile for cholesterol microlithiasis varies among medical institutions, although a widely accepted standard is polarized-light microscopy. An example of the foregoing protocol for bile analysis is provided in Cynthia W. Ko, John H. Sekijima, M.D., and Sum P. Lee, M.D., Ph.D., xe2x80x9cBilliary Sludge,xe2x80x9d Annals of Internal Medicine, Vol. 130 (1999), pp. 301-311. Bile is aspirated endoscopically from the patient after the administration of cholecystokinie (xe2x80x9cCCKxe2x80x9d). The CCK stimulates contraction of the gall bladder and relaxation of the sphincter of Oddi, thereby causing bile to flow out of the gall bladder, through the bile duct, and into the duodenum, where 2 to 5 milliliters of duodenal fluid, including bile, is collected. The sample is placed in a centrifuge tube and spun at 3000 g for 15 minutes.
Several microliters of sediment, suspended in a drop of distilled water, are transferred to a glass slide and examined by polarizing microscopy. When examined in this manner, cholesterol monohydrate crystals appear as bright, rhomboid-shaped plates or clumps of plates against a dark background. Ko et al. regard a positive test as finding more than two crystals of any type in a 100xc3x97magnified field or more than four crystals per sample.
The accuracy of the test results been called into question due to a lack of consensus in the medical community regarding the proper temperature at which the bile sample should be maintained prior to microscopic analysis. Some experts contend that cooling to this temperature inhibits bacterial growth during the unavoidable interval between drawing the sample and conducting the assay, while others maintain that cooling artificially induces the formation of precipitates that were not present in the sample in vivo. The accuracy of the test results thus depends whether the sample was cooled, and whether cooling ensures accuracy or is actually inimical to it.
In view of the foregoing, it can be seen that a need exists to provide a device that allows attending medical personnel to test for the presence of microlithiasis in bile during ERCP. More particularly, there is a need for a device that provides for relatively immediate microcrystal detection in bile extracted from a living organism. Such a device would allow the assay to be performed under known, controlled, and near life-like conditions during a period when further interventional treatment, i.e., sphincterotomy, could be immediately administered. Performing the assay immediately after the bile sample is withdrawn from the patient would moot the controversy over whether the bile sample should be cooled to inhibit bacterial growth, or whether such cooling in fact compromises the accuracy of the assay by inducing microcrystal precipitation in the sample.
Furthermore, having the results of an assay immediately available to the attending physician during ERCP would allow the physician, if warranted by the assay results, to immediately proceed with the administration of further interventional treatment. Since the diagnosis and treatment could be performed during the same ERCP, the patient would avoid the risks and discomfort associated with a second ERCP.
As may be seen from the foregoing, there presently exists a need in the art to rapidly detect crystalline materials in a fluid sample, e.g., bile, withdrawn from a patient undergoing ERCP, and thereby overcome the shortcomings, disadvantages and limitations of the prior art. The present invention fulfills this need in the art.
Briefly, the present invention is an apparatus for rapidly detecting crystalline materials such as cholesterol microcrystals in a fluid sample, e.g., a bile sample, withdrawn from a patient undergoing ERCP. The fluid sample flows through a transparent flow channel and into a collection reservoir. An interrogating light beam is polarized by an optical polarizer into a well-defined first plane of polarization. The transparent flow channel is situated orthogonal to the polarized interrogating light beam. The polarized light beam passes through the fluid sample as the fluid flows through the flow channel. The light beam is then directed to a second polarizer that passes only light having a plane of polarization that has undergone some degree of rotation relative to the first plane of polarization.
The birefringence of crystalline materials, such as microcrystalline cholesterol of times contained in the bile of patients suffering from pancreatitus, rotates the plane of polarization of the polarized light beam as it passes through the fluid sample. The presence of such microcrystals thus causes a portion of the interrogating beam to pass through the second polarizer and impinge an electronic photo-detector located in the path of the beam. The electronic photo-detector signals the detection of birefringent microcrystals by generating voltage pulses.
The device rapidly displays the quantitative results of the assay. It can be further configured to bar-code scan a patient""s medical record number; find, retrieve and print out the designated medical record; and enter the record together with the results of the microcrystal detection test directly into a hospital""s patient database via a built-in network interface.
A disposable fixture comprised of the flow channel and collection reservoir is adapted for removable insertion into an interrogation cradle. The fixture also includes some of the optics. The cradle includes the remainder of the optics and the electronic photo-detector. Attachment of the fixture to the cradle fixes the position of the flow channel relative to the interrogating beam, the optics, and the electronic photo-detector. In particular, the cradle keeps the flow channel centerline orthogonal to the interrogation beam. In addition, the foregoing configuration keeps the sample fluid contained within the fixture during its interrogation, and provides for its convenient disposal along with the detached fixture after the test is completed.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.